2025 Becomes Third-Warmest Year as the World Nears Threshold — Here’s Why

The planet recorded its third-warmest year on record in 2025, and average temperatures have exceeded 1.5 degrees Celsius of global warming over three years, the longest period since records began, EU scientists said on January 14.

The UK Met Office, Britain's national weather service, also confirmed its own data ranked 2025 as the third-warmest in records going back to 1850. Recording a mean temperature of 10.09 degrees Celsius, 2025 now joins 2022 and 2023 in the top three warmest years since 1884, the UK Met Office reported. The World Meteorological Organisation is expected to publish its temperature figures later on January 14.

The hottest year on record was 2024.

Rising Temperatures, Worsening Extremes

According to the European Centre for Medium-Range Weather Forecasts (ECMWF), the planet recently experienced its first three-year period in which the average global temperature was 1.5 degrees Celsius higher than that of the pre-industrial era. This is the threshold beyond which scientists anticipate that global warming will have detrimental effects, some of which are irreversible.

"1.5 C is not a cliff edge. However, we know that every fraction of a degree matters, particularly for worsening extreme weather events," Samantha Burgess, strategic lead for climate at ECMWF told Reuters.

Under the 2015 Paris Agreement, governments committed to attempting to prevent global warming of more than 1.5 degrees Celsius, which is defined as a decades-long average temperature relative to the pre-industrial era.

However, because of their inability to cut greenhouse gas emissions, that threshold may now be exceeded before 2030, which is ten years earlier than anticipated when the Paris Agreement was signed in 2015, reported Reuters citing ECMWF.

What the 1.5 degrees Celsius Limit Means

The 1.5 degrees Celsius threshold refers to limiting the rise in world’s average surface temperature to no more than 1.5 degrees Celsius above the pre-industrial levels by 2100. Pre-industrial levels are used as a baseline because large-scale fossil fuel emissions began with the industrial revolution, when carbon locked in coal, oil and gas started penetrating the atmosphere.

The International Panel on Climate Change (IPCC) uses the 1850-1900 period as the baseline, as it is the earliest period with reliable near-global temperature measurements. While some warming from human activity had already occurred by then, consistent historical data is essential for accurately measuring today’s changes.

The common baseline ensures scientists, politicians, activists and policymakers refer to the same benchmark.

The 1.5 degrees Celsius threshold was set as a target under the Paris Agreement in 2015, in which 195 countries committed to keeping global warming “well below” 2 degrees and striving to limit it to 1.5 degrees Celsius.

Citing IPCC’s analysis in 2023, BBC reported that there would be a 50% chance of the world committing itself to a rise of 1.5 degrees Celsius by the mid-2030s. However, a new analysis taking into account more recent data indicates that we could reach this threshold sooner as early as 2029.